A geocoin is a metal or wooden coin minted in similar fashion to a medallion, token coin, military challenge coin or wooden nickel, for use in geocaching. The first geocoins were developed by Jon Stanley (aka moun10bike) as a signature item to be placed in caches.
Many of them are made to be trackable on various websites to be able to show the movement around the world and visitors to be able to leave comments when they find the coin.
A geocoin typically has a diameter of 1.5 inches (38 mm) to 2 inches (51 mm) and a thickness between 0.098 inches (2.5 mm) and 0.16 inches (4 mm). Coins with the size of 1 inch (25 mm) are called microcoins, because they fit into microcaches (e.g. film canister). The smallest geocoins with a diameter of 0.5 inches (13 mm) are called nanocoins, and have been sold since 2009. If the diameter is larger than 3 inches (76 mm) the geocoin is called macrocoin. It has the famous saying of "that's not a coin it's an anchor".
September 30, 2001: The first trackable geocoin released was the Moun10Bike Version 1 Geocoin #002.The Moun10Bike Version 1 Geocoins are the most sought-after geocoins in existence. They are all displayed on geocaching.com as owned by Moun10Bike and he has strictly forbidden their sale; however, unscrupulous or ignorant persons may list the coin for sale on auction sites such as eBay, fetching prices in the thousands of USD. When he finds that a coin has been sold without permission, he has the coin locked so it is no longer trackable.http://www.geocaching.com/track/details.aspx?tracker=TBD600
March 2002: The first geocoin that was produced and sold to the public to collect and release was the Canadian geocoin.
2003: The first USAGeocoin was released for sale, making it one of the first geocoins that one can buy, release, and track online without minting an exclusive personal design. The proposed 2002 design was never made.
2005: Geocaching.com permitted any geocaching.com user to purchase tracking numbers for approved designs, fueling a sudden surge in number of coins. Minimum purchase was initially set at 1000 tracking numbers.
Fall 2006: Groundspeak reduced the minimum purchase of tracking numbers, and the minimum number of coins minted to obtain a unique icon, to 250. The drop in the cost to create a geocoin with a unique icon fueled a 'geocoin craze' with hundreds of new personal, group and increasingly purely commercial designs minted.
February 17, 2007: The First Annual Geocoinfest was held in Temecula, CA. This event brought hundreds of geocoin collectors together for the first time in a mass event, with many exclusive coins being given away or traded.
Fall 2007: Geokrety.org began a free tracking service, Geokrety, for coins and other items, with full support for geocaching sites such as Opencaching.us and partial support for other geocaching sites.
March 4, 2009: Geocaching.com further reduced the minimum number of codes for purchase to 50, and the minimum number of coins eligible for a custom icon to 50.